Use the new "pip-in" and "pip-out" GNOME symbolic icons if user theme has them for enter/leave floating mode button. When icon is unavailable on the host, old icon will be used instead.
This avoids D&D controllers clash and allows to freely customize how maximize, minimize and close buttons work (differently for e.g. web application) and where are they placed
The "clapper_src" directory name was unusual. This was done to make it work as a widget for other apps. Now that this functionality got removed it can be named simply "src" as recommended by guidelines.
